Global Courant
The effort to save one of Canada’s most endangered freshwater fish now includes electronic tracking of captive-bred specimens released into the Nova Scotia watershed, which is home to the world’s only remaining wild population.
Last week, a final batch of 30 tagged Atlantic whitefish was released into the Petite Rivière system behind the town of Bridgewater on the county’s south coast.
“We released fish in different parts of the system, the lake part, the river part and also in the estuary in salt water,” said Jeremy Broome, a biologist with Fisheries and Oceans Canada who is assigned to the recovery team.
“So looking at which of those might yield the best survival is important to us.”
Tags inserted with needle
Tiny transponder tags were inserted with a hypodermic needle into 150 year-old fish spawned at Dalhousie University’s Aquatron research facility in Halifax.
The fish were anesthetized, given a week to recover, and released at various locations in the watershed. Fish were released into the estuary after they got used to salt water.
Devices installed at narrow points along the river system send a signal when a tagged fish swims by.
“We’re testing different approaches, dividing our eggs into different baskets to see what works best,” Broome said.
“If we can find that survival is better with release into the estuary, we see more fish coming back from that strategy, which would be an indication that we would like to continue with that approach.”
Enclosed by land for centuries
An ancient relative of the Atlantic salmon, this species of whitefish is anadromous by nature, meaning they are born in fresh water, travel to the ocean and return to spawn.
They only survived in the Petite Rivière basin, which was enclosed by a dam for a century and serves as a water supply for the town of Bridgewater.
A fish ladder was installed there in 2012.
The recovery team hopes to see evidence that 1,100 unlabeled juveniles released last year and tagged in 2023 will return to spawn in the next two years.
An ancient relative of the Atlantic salmon, this species of whitefish is anadromous by nature, meaning they are born in fresh water, travel to the ocean and return to spawn. (Submitted by Ministry of Fisheries and Oceans)
Why the Atlantic Whitefish is in Trouble
Nearly 40 years ago, the species was the first fish in Canada to be rated endangered by the Committee on the Status of Endangered Wildlife.
The whitefish faces several threats, including warming waters and invasive smallmouth bass and chain pickerel being introduced to the watershed.
Atlantic whitefish are now so scarce that when found, the fry are taken an hour’s drive to the Aquatron, where a captive breeding program is underway.
Unlike previous years, no juveniles or larval minnows were caught in traps installed anywhere in the system this spring.
Dalhousie’s Aquatron now contains more Atlantic whitefish than exist in the wild.
“Without the brood stock that we were able to develop in that facility and the offspring that are coming out of there now, we really would be out of options. We’re still not in a great place, but without that facility and without that program we would be we are in a very difficult position,” said Broome.
Looking for another home
The salvage team is also looking for other watersheds in Nova Scotia where the critically endangered species could be introduced and survive.
Several candidate sites have been identified and surveys are planned for this summer. Consultation is the next step.
“I think we’ve come to a point where we need to step up and start trying these things,” he said.
The salvage team is also looking for other watersheds in Nova Scotia where the critically endangered species could be introduced and survive. (Submitted by Ministry of Fisheries and Oceans)
A 20-year recovery carousel
After first being declared an endangered species in 2003, a captive breeding program was established at the Mersey Biodiversity Center in Nova Scotia as part of a government-mandated recovery strategy.
The program was discontinued and the Mersey Diversity Center was literally bulldozed under the Harper government in 2013.
A few months later, the voracious invasive chainpike was discovered in the Petite Rivière watershed, where the remaining wild population was located.
Thousands of whitefish farmed at the diversity center had been released into a lake behind Burnside industrial park in Dartmouth. None survived.
Between 2014, when the chain pickerel settled, and 2018, no mature whitefish were seen alive.
Dalhousie comes to the rescue
Since then, Dalhousie stepped in to offer his Aquatron facility, first as a Noah’s Ark to save the species from extinction and later to host a captive breeding program.
The university has also been involved in the construction of a riverside nursery, a miniature part of the diversity center demolished by the previous federal government.
Even the reintroduction into the Petite Rivière system is a repeat of the work of the canceled captive breeding program.
Still, Broome remains hopeful.
“This is real, this is a species of fish from Nova Scotia. It is only found here, only in the province, the only place in the whole world,” he said.
“So it’s up to us to do something about it. It’s up to us to protect and sustain the planet.”
